Reservoir Simulation Study and Optimizations of CO₂ Huff-n-Puff Mechanisms in Three Forks Formation

An in-depth description of the objectives of rich gas cyclic huff 'n' puff in the Three Forks of the Williston Basin, as well as the design, field operations, production, pressure, and other surveillance results, is provided in this case study. To summarize, the overall purpose of the enhanced oil recovery (EOR) and CO₂ storage, a case study, was to discover important performance indicators of cyclic gas injection, which would then be used to construct a commercial field scale EOR method. To achieve these objectives, a fully designed well in the Three Forks tight oil play was tested vertically and laterally for the potential to confine gas inside the target intervals and create pressure to induce a miscible displacement process. In this paper, a detailed reservoir model was built to investigate the CO₂ huff-and-puff process for enhancing oil recovery (EOR), and to understand the impact of different parameters on the CO₂ EOR performance in different scenarios. The model includes an area of well-characterized Three Forks formation and fracture characteristics with actual production data from the field for accurate history matching and forecasts. The effects of cycle number, injection and soaking period, permeability, reservoir bottom hole pressure, and CO₂ molecular diffusion are investigated to optimize the reservoir's CO₂ EOR performance. The findings suggest that CO₂ diffusion is essential in enhancing oil recovery from tight oil reservoirs as the recovery factor (RF) without diffusion was 12%, including the diffusion coefficient the RF increased by 4%. Also, the bottom hole pressure significantly impacts the recovery factory. Furthermore, the CO₂ huff-n-puff technique is more beneficial in tight oil formations with high permeability and more CO₂ injected in a short soaking period. Significant design and operational efficiencies were discovered during this well simulation for gas injection test in the Three Forks play that will benefit an economically feasible fieldscale project. For example, the schedule of injection and soaking period permitted gas injection operations to be carried out without modifying wells' operation pressure. Cycling in a short soaking time makes it possible to perform injection/production conversions at the lowest possible cost. It is also possible that including the diffusion coefficient in the simulation will have better gas injection conformity across the horizontal completed intervals.